Isomerization



Patented Apr. 30, 1946 ISOMERIZATION John KellettJII, Milton M. Marisic,and Arlie A. N. J., assignors to Socony- Vacuum Oil Company,Incorporated, a corporation of New York No Drawing. Application January29, 1944,

Serial No.

Claims. (Cl. 260-6835) This invention relates to vapor phaseisomerization of saturated paraflin hydrocarbons and is particularlyconcerned with conversion of saturated hydrocarbons having straight orslightly branched chains to isomers thereof having a higher degree ofchain branching.

The utilization of isoparaflins for alkylation reactions involvingcondensation with olefins in the presence of a catalyst and the'increased need of higher octane fuel has encouraged interest inprocesses of isomerization. Of particular interest are conversions ofnormal butane to isoisomerized will be initiated in the presence ofcracking catalyst used.

It is essential to the success of the operation that substantialuper-atmospheric pressures beapplied. In general, the pressures at whichthe process is operative are in excess of 500 pounds butane to be usedin 'alkylation and conversion of low octane value hydrocarbons to morehighly branched-chain hydrocarbons of better fuel value. In the lattercategory, it may be mentioned that isopentane is a very valuablecomponent of avia'tion fuels and isomerization of normal heptanes andoctanes for fuel purposes is also of major interest. Thepresentinvention provides a com-' mercially practicable process for conversionof saturated hydrocarbons in general, having four or more carbon atomper molecule, to isomers of the material charged. It is, of course,preferable to; charge a straight-chain or slightly branched-chainhydrocarbon at the present time since the value of these hydrocarbons asfuels is closely related to the degree of chain branching.

The majority of the processes proposed for commercial operation involvetheuse of metal halides, particularly aluminum chloride and aluminumbromide as catalysts. Reaction times required by these catalysts areunduly long and the catalyst i rapidly contaminated to a stage where itis no longer economically efiective. Regeneration of such catalysts assuch is impossible at the present time, although the aluminum may brecovered and converted again to the chloride. It has been proposed toutilize metals of the iron group deposited on specially treated clay.This process also requires fairly long contact times and theregeneration of any catalyst having a metallic element as an essentialconstituent requires an'expensive reduction step such as hightemperature treatment with hydrogen.

According to the present invention, thehydrocarbons to be converted arecontacted in vapor phase with an inorganic oxide adso'rbent materialhaving a substantially-high cracking ac tivity as measured by conversionof gas oil under moderate crack ng conditions. The temperatures employedaccording to the present invention are in the neighborhood of theminimum temperature at which cracking of the hydrocarbon to be persquare inch, preferably 700 to 1000 pounds per square inch. It appearsthat extremely high pressures do not materially aid the course of theisomerization reaction, but, on the other hand, no detrimental efiect ofsuch high pressures has been found. It appears that maximum pressuresfor the process are dictated primarily by limitations of the apparatusused.

The catalyst may be any of the known adsorbent compositions whichconsist'essentially of inorganic oxides, such as silica, alumina,thoria, ceria,'bery1lia and the like, preferably in the form ofcombinations of two or mor oxides. Of these of the other inorganicoxide'cracking' compositions, silica alumina is typical, and since thiscombination has been the most extensively studied for crackingreactions, it will be treated hereinafter as typical of the operativecatalysts. It i to be understood, however, that any catalysts conformingto the definitions hereinafter may be utilized in the same manner'assilica alumina.

The catalyst may be either a natural or synthetic composition, forexample, the natural clays which hav been activated to give themsubstantial cracking activity. Among the synthetic catalysts suitablefor the present inven-'- tion, a distinction must be recognized betweenprecipitates on the one hand and gels on the other. In general, the gelshave a considerably higher activity than do corresponding precipitates.Preparation of the synthetic'catalyst; u'n-- der such conditions thatprecipitate will be formed and included in a subsequent gel, will resultin decrease in activity commensurate with the amount of precipitateformed. Preferably, a

true gel catalyst is usedand superior result are obtained when thatcatalyst is formed in accordance with copending application Serial No.461,454, filed October 9, 1942, by Milton M, Marisic, According to thatprior application, a gelable sol having a pH of 2.5 to .10 is extrudedinto the top of a column of oil wherein it separates into globules. Theglobules set to a firm hydrogel while falling through the oil and areremoved as hydrogel spheroids which are then washed with water,base-exchanged to remove alkali metals, dried and heat treated attemperatures upwards of 1000 F.

The catalyst to be used according to the prestemperatures of about 700to 1000 desired isomers and this result will be obtained .mina f 12 to1.

ent invention should have a cracking activity or at least 25% asmeasured by conversion or Oklahoma City Gas 011 having an A. P. I.gravity of 35.8 and a boiling range of 471 to 708 F. to gasoline havingan end point of 410 F. by passing said gas oil through said catalyst at800. F., substantially atmospheric pressure and a liquid feed rate of1.5 volumes of said gas oil per volume of catalyst per hour fortwenty-minute periods between regenerations.

The activity or catalyst for isomerization of paraflin hydrocarbonsseems to be parallel to the cracking activity. In general, the contacttime will vary inversely as the temperature employed F. being suitablefor most purposes. The conditions should be adjusted in order to obtaina good yield of the monium chloride pelleted and finally heat treat d at105 for six hours.

EXAMPLF Catalyst 2 is a hydrated silica alumina gel having a molar ratioof silica The gel was prepared by mixing solutions of sodium silicate,aluminum sulfate and hydrochloric acid to form a sol having a pH of0.27, which, on standing, set to a hydrogel. The hydrogel was brokeninto particles or about one inch in diameter andwashed until free ofacid and soluble salts, then dried at 180 F. to constant weight andgradually heated to 1050 F. at which temperature the gel was maintainedfor four hours. The gel catalyst was in the form of fragments of 6 to14mesh size. I

EXAM LEIII if the pressure is not substantially below 500 silica-aluminagel havpounds per square inch at a temperature not substantially belowthat at which cracking of the hydrocarbon charge is initiated in thepresence of the catalyst employed. Fol-many purposes, substantialcracking is not particularly undesirable since the degradation productsare largelyisoparafllns and therefore valuable in many hydrocarbonsyntheses. As the art well knows, the resistance of parafllns tocracking is related to the molecular weight-the higher paraflinscracking at a substantially lower temperature than hydrocarbons having alesser number of carbon atoms.

In general, it is desirable that the charge stock undergoing theisomerization reaction, according to this invention, shall be ofrelatively narrow boiling range in order that the conditions maybecontrolled to give maximum conversions of each constituent. Thus, Weprefer that the highest boiling hydrocarbon and the lowest boilinghydrocarbon forming substantial portions of the charge stock shall notdifler by more than one carbon atom.

The advantages oi the invention and the manner in which isomerizationyields vary with-cracking activity will be apparent. from the followingspecific examples:

Catalyst 3 is a hydrated I ing a molar ratio of silica to alumina of 16to 1. This catalyst was prepared in the form oi spheroidal particles bymixing solutions of sodium silicate, aluminum sulfate and sulturic acidto form a colloidal solution having a pH of 8.5 and a gelation time of 5seconds. The sol prior to gelatlon was extruded into oil to formhydrogel beads, which were washed with water at 95 F. until free ofsoluble salts, base-exchanged with aluminum sulfate solution, washedagain, dried and heat treated at 1100 F. for four hours.

nxamhn 1v Catalyst 4 was prepared in a manner similar to the descriptionfor catalyst 3. The essential difference between the two catalysts was amore drastic heat treatment applied to the former catalyst, whichconsisted of passing a mixture of 5% steam and 95% air over the catalystat a temperature of 1425 F. for ten hours. The chemical composition ofthe two catalysts is the same.

. EXAMPLE V Catalyst 5 is a hydrated silica-alumina gel having a molarratio of silica to alumina of 55 to 1. This catalyst was prepared inhead form from solutions of sodium silicate, sodium aluminate andsulfuric acid. The pH of the colloidal solution was 5.4 and seconds. Thehydrogel beads were processed in the same manner as catalyst 3 exceptthat tem- EXAMPLE I Catalyst No. 1 is a hydrated silica-aluminacomposition having a molar ratio of silica to alu- This catalyst wasprepared by mixing a solution or sodium aluminate and sodium silicatewith a solution or ammonium sulfate to form a gelatinousprecipitatehaving a pH of 9.5. The precipitate was dried to a waterconbase-exchange material was NHiCl.

Data on the isomerization 01 normal pentane tent of 20%, then ground toa powder, washed over each of the above catalysts is shown in the freeor soluble salts, base-exchanged with arnfollowing table:

a I Turn 1 High. temperature pressure ismnerieatio'n datatheisomerization of npentane Catalyst Operation conditions Pod. analysis ofliqud product, vol. per cent No. Appa'r Prosi Nor- Craolr- Space Contactt Tom sure. On-stream Prolsobnlsobuland's Isnpen mnl Real 35%; d n- F?lbs. fig, time. m'in. 9." pane tone tone butenes tone :1- duo m SI e1--.- 47 0550 an 1,000 1.0 120 as s0 0 2.-.. 10-- 0010 020 1,000 1.0 40a0 4.1 1.1 89.7 5.1 0.-.- 49 am 815 1,000 1.0 120 as 0.0 21.5 no 1.0 touse: 000 1.000 1.0 40 a1 0.8 as as 22.0 00.1 2.4 a0 0002 810 1,000 1.0120 as, 0s 21 a1 0.1 no 210 05.2 as 0-..- 41 V 0010 s50 1,000 1.0 120 asm0 I Undetermined. 1 Total degradation products.

to alumina of 20 to l.

perature of the wash water was F aud the solution, washed again, dried,I

the gelation time was twenty We claim: l. A process for theisomerization of paramn hydrocarbons having at least four carbon atomsper molecule to isomers thereof having the same number of carbon atomsbut difierent chain wherein the highest boiling and the lowest boilinghydrocarbon present in substantial amounts differ by not more than onecarbon atom and contacting the hydrocarbon vapor at a temperature ofabout 700 to about 1000 E. and a pressure not substantially below 500lbs. per square inch with a solid porous adsorbent contact massconsisting substantially of inorganic oxides and having a crackingactivity of at least about 25% as measured by percentage conversion ofOklahoma City Gas Oil having an A. P. I. gravity of 35.8 and a boilingrange of 471 to 708 F. to gasoline having an end point of 410 F. bypassing said gas oil through said catalyst'at 800 F., substantiallyatmospheric pressure and a' liquid feed rate of 1.5 volumes of said gasoil per volume of catalyst per hour for periods of twenty minutesbetween regenerations; said temperature being in the neighborhood of theminimum temperature at which cracking of the said paraffin hydrocarbonswill be initiated in the presence of said catalyst; thereafter removinghydrocarbons from contact with said catalyst and separating therefromisomers of the parafiin hydrocarbons contacted with said catalyst asaforesaid.

2. A process for the isomerization of paraffin hydrocarbons having atleast four carbon atoms per molecule to isomers thereof having the samenumber of carbon atoms but different chain structure with only minordecomposition of said paraffin hydrocarbons to hydrocarbons having adifferent number of carbon atoms which comprises vaporizing a mixture ofhydrocarbons wherein the highest boiling and the lowest boilinghydrocarbon present in substantial amounts differ by not more than onecarbon atom and contacting the hydrocarbon vapor at a temperature ofabout 700 to about 1000 F. and a pressure not substantially below 500lbs. per square inch with a solid porous adsorbent contact massconsisting substantially of silica and atleast one metal oxide andhaving a cracking activity of'at least about 25% as measured bypercentage conversion of Oklahoma City Gas Oil having an A. P. I.gravity of 35.8 and a boiling range of 471 to 708 F. to gasoline havingan end point of 410 F.'by passing said gas oil through said catalyst at800 F., substantially atmospheric pressure and a liquid feed rate of 1.5volumes of said gas oil per volume of catalyst per hour for periods oftwenty minutes between regenerations; said temperature being in theneighborhood of the minimum temperature at which cracking of thesaid-parafiin hydrocarbons will beinitiated in the presence of saidcatalyst; thereafter removing hydrocarbons from contact with saidcatalyst and separating therefrom isomers of the paraflin hydrocarbonscontacted with said catalyst as aforesaid.

3. A process for the isomerization of paraflin hydrocarbons having atleast four carbon atoms per molecule to isomers thereof having the samenumber of carbon atoms but different chain structure with only minordecomposition of said paraffin hydrocarbons to hydrocarbons having adifferent number of carbon atoms which comprises vaporizing a mixture ofhydrocarbons wherein the highest boiling and the lowestboiling'hydrocarbon present in substantial amounts differ by not morethan one carbon atom and contacting the hydrocarbon vapor at atemperature of about 700 to about 1000 F. and a pres sure notsubstantially below 500 lbs. persq'uare inch with a solid porousadsorbent contact, as consisting substantially of a dried gel of mergein oxides and having a cracking activity of at least about 25% asmeasured by percentage conversion of Oklahoma City Gas Oil having an A.P. I; gravity of 35.8 and a boiling range of 471 to 708 F. to gasolinehaving an end point of 410 F. by passing said gas oil through saidcatalyst at 800 F., substantiallyatmospheric pressure and a liquid feedrate of 1.5 volumes of said gas oil per volume of catalyst per hour forperiods of twenty minutes between regenerations; said temperature beingin the neighborhood of the minimum temperature at which cracking of thesaid parafiin hydrocarbons will be initiated in the presence of saidcatalyst; thereafter removing hydrocarbons from contact with saidcatalyst and separating therefrom isomers of the parafiin hydrocarbonscontacted with said catalyst as aforesaid.

4. A process for the isomerization of paraffin hydrocarbons having atleast four carbon atoms per molecule to isomers thereof having the samenumber of carbon atoms but different chain structure with only minordecomposition of said paraifin hydrocarbons to hydrocarbons having adifferent number of carbon atoms which comprises vaporizing a mixture ofhydrocarbons wherein the highest boiling and the lowest boilinghydrocarbon present in substantial amounts differ by not more than onecarbon atom and contacting the hydrocarbon vapor at a temperature ofabout 700 to about 1000 F. and a pressure not substantially below 500lbs. per square inch with a solid porous adsorbent contact massconsisting substantially of a dried gel of silica end point of 410 F. bypassing said gas oil through said catalyst at 800 F., substantiallyatmospheric pressure and a liquid feed rate of 1.5 volumes of said gasoil per volume of catalyst per hour for periods of twenty minutesbetween regenerations; said temperature being in the neighborhood of theminimum temperature at which cracking of the said paramn hydrocarbonswill be initiated in the presence of said catalyst; thereafter removinghydrocarbons from contact with said catalyst and separating therefromisomers of the paraffin hydrocarbons contacted with said catalyst asaforesaid.

5. A process for the isomerization of paramn hydrocarbons having atleast four carbon atoms per molecule to isomers thereof having the samenumber of carbon atoms but difierent chain structure with only minordecomposition of said parafin hydrocarbons 'to hydrocarbons having adifferent number of carbon atoms which comprises vaporizing a mixture ofhydrocarbons wherein the highest boiling and the lowest boilinghydrocarbon present in substantial amounts differ by not more than onecarbon atom and contacting the hydrocarbon vapor at a temperature ofabout 700 to about 1000 F. and a presstu'e not substantially below 500lbs. per square catalyst at 800 F., substantially atmospheric pressureand a liquid feed rate of 1.5 volumes of said gas oil per volume ofcatalyst per hour for periods of twenty minutes between regenerations;

said temperature being in the neighborhood of the minimum temperature atwhich cracking or the said paraiiln hydrocarbons will be initiated inthe presence of said -catalyst; thereafter removing hydrocarbons fromcontact with said catalyst and separating therefrom isomers of therparamn hydrocarbons contacted with said catalyst as aforesaid.

- JOHN KELLE'IT, III.

MILTON M. MARISIC. ARI-IE A. OKELLY.

